Maturity is realizing that Chaghan valued Rin more than Altan
Chaghan never truly believed he could save Altan even though he did try to fix him. He understood him too well Altan was raised as a weapon, shaped by trauma, rage, and the sheer inevitability of self-destruction. Brilliant, powerful, and doomed. And Chaghan, for all his strength, knew there was nothing left in Altan he could reach. His frustration with him was pragmatic, he expected disaster, and disaster came (And we can see all of that in their final argument)
He didn’t trust her, and he certainly wasn’t on her side (he literally says that ) but he recognized something in her that Altan had lost long before the ability to choose. Rin still had a future that wasn’t predetermined by pain. She was unstable, yes, but aware, and that awareness made her dangerous in a way Altan never was
Chaghan valued Rin not because he felt affection, but because he saw potential.He could guide her, warn her, even challenge her,and yes, fight her too
Their dynamic is full of friction, but it’s also full of mutual respect. Chaghan never saw Rin as an inferior, he helped her most of the time, and you can think "it was because of his loyalty to Altan" At first, yes, it was because he wanted to continue Altan’s legacy and wanted Rin to follow it too
But he realizes that he is everything she has
("Do you have to come?" she asked
"You can’t do it alone. I’m all you’ve got. You have to trust me")
And that is why her mistakes hurt him more
Chaghan valued Rin more because she had a chance to be more. And his disappointment isn’t about her failures it’s about the loss of the possibility he saw in her. Altan’s tragedy was inevitable. Rin’s, in Chaghan’s eyes, didn’t have to be